18 



IIAYDEN : GEOT/IGY OP NOTtTIIEItN AFGHANISTAN. 



At about 4 miles to the north of Kabul, across the c/iaman 1 and near 

 the village of Khoja Bogra, is a small hillock of crystalline limestone 

 with a little gneiss and some bands of epidiorite. The limestone is 

 interesting as containing bowenite, the hard variety of massive serpen- 

 tine. It is apple-green in colour and the large patches, several inches 

 in width, show up very beautifully on the background of white and 

 creamy marble. 



Like the metamorphic rocks of the Siah Koh, those of Kabul 

 Age of the crystalline present a difficult problem in the determination of 

 their age. Assuming that between the Asmai 

 heights and Khurd Kabul we are dealing with a single group of rocks, 

 we have at least the means of fixing an upper limit to their age, for 

 they are overlain unconformably on " Khurd Kabul station" (11,143 

 feet) by fossiliferous Upper Paleozoic (Upper Carboniferous or Permian) 

 limestone (infra, p. 21). They cannot, therefore, be younger than 

 Carboniferous. In the other direction, however, there is no limit assign- 

 able. The unconformity is very pronounced, and the overlying fossili- 

 ferous limestones show no signs of metamorphism ; presumably, there- 

 fore, the schistose series had already been metamorphosed before the 

 Upper Palaeozoic transgression took place, and one would naturally con- 

 clude that the difference in age represented by the unconformity is very 

 considerable. Other considerations also lead us in the same direction, 

 and one is tempted to see in the cupriferous mica-schists and limestones 

 and in the quartz-hematite schist of Keshlak in Masai, representatives 

 of our Indian Dharwars. 



On the other hand, the resemblance of this crystalline series to the 

 Dharwars is no greater than that of the Jagdallak limestones to the 

 corresponding members of the Archaean group in the Peninsula and 

 Burma, and if we are to follow Mr. Griesbach in regarding the rocks of 

 the Siah Koh as Palaeozoic, we may equally well refer the crystalline 

 schists and gneisses of Kabul to the same group. Justification for such 

 a course might perhaps be sought in the conditions prevailing in the 



1 A broad reedy swamp. 



